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Study finds lifelong neurogenesis in the hippocampus, but rates decline with age and, especially, Alzheimer’s disease

Recent, imma­ture neu­rons (in red) and old­er, mature neu­rons (in blue) in the hip­pocam­pus of a 68-year-old’s brain. Cred­it: CSIC


Old brains still make neu­rons, study finds, offer­ing a pos­si­ble way to pro­tect against Alzheimer’s (STAT):

Reports of old brains’ decrepi­tude have been great­ly exag­ger­at­ed, sci­en­tists report­ed on Mon­day, unveil­ing results that con­tra­dict a much-dis­cussed 2018 study and instead sup­port the idea that human gray mat­ter is capa­ble of gen­er­at­ing new neu­rons up to the ninth decade of life.

The research, pub­lished in Nature Med­i­cine, also found that old brains from peo­ple with­out demen­tia have much high­er rates of such neu­ro­ge­n­e­sis than do the brains of peo­ple with Alzheimer’s dis­ease, offer­ing a new clue to a field that is des­per­ate for new ideas…

In a 43-year-old brain, for instance, the sci­en­tists mea­sured rough­ly 42,000 new neu­rons per cubic mil­lime­ter of hip­pocam­pus (approx­i­mate­ly the vol­ume of nine grains of table salt). An 87-year-old had 20,000 new neu­rons per cubic mil­lime­ter…

Although Llorens-Martín and her col­leagues did not have enough brains of the same age to make defin­i­tive com­par­isons of indi­vid­ual neu­ro­ge­n­e­sis rates, they saw hints of per­son-to-per­son vari­a­tion. Among peo­ple in their 60s with­out Alzheimer’s, she said, rates of neu­ro­ge­n­e­sis ranged from about 30,000 to 40,000 new neu­rons per cubic mil­lime­ter of hip­pocam­pus; in 80-some­things, it was 20,000 to 30,000.

If you can increase the rate of neu­ro­ge­n­e­sis, it might be pro­tec­tive” against Alzheimer’s, she said.

The New Study:

Adult hip­pocam­pal neu­ro­ge­n­e­sis is abun­dant in neu­ro­log­i­cal­ly healthy sub­jects and drops sharply in patients with Alzheimer’s dis­ease (Nature Med­i­cine). From the abstract:

  • The hip­pocam­pus is one of the most affect­ed areas in Alzheimer’s dis­ease (AD) … By com­bin­ing human brain sam­ples obtained under tight­ly con­trolled con­di­tions and state-of-the-art tis­sue pro­cess­ing meth­ods, we iden­ti­fied thou­sands of imma­ture neu­rons in the DG of neu­ro­log­i­cal­ly healthy human sub­jects up to the ninth decade of life. These neu­rons exhib­it­ed vari­able degrees of mat­u­ra­tion along dif­fer­en­ti­a­tion stages of AHN (Note: adult hip­pocam­pal neu­ro­ge­n­e­sis). In sharp con­trast, the num­ber and mat­u­ra­tion of these neu­rons pro­gres­sive­ly declined as AD advanced. These results demon­strate the per­sis­tence of AHN dur­ing both phys­i­o­log­i­cal and patho­log­i­cal aging in humans and pro­vide evi­dence for impaired neu­ro­ge­n­e­sis as a poten­tial­ly rel­e­vant mech­a­nism under­ly­ing mem­o­ry deficits in AD that might be amenable to nov­el ther­a­peu­tic strate­gies.

The New Study in Context:

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Categories: Cognitive Neuroscience, Education & Lifelong Learning, Health & Wellness

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As seen in The New York Times, The Wall Street Journal, BBC News, CNN, Reuters,  SharpBrains is an independent market research firm tracking how brain science can improve our health and our lives.

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